This invention relates to machines and processes for manufacturing concrete products, such as concrete pipe, manholes, catch basins, and the like, and more specifically, the invention relates to the “dry-cast” method of manufacturing concrete products which requires a system for providing vibration to the core of the concrete mold during the fill and pressure-head cycles of the manufacturing process.
In the dry-cast method of manufacturing, concrete vibration is necessary to consolidate the concrete products prior to curing. The inner mold, or core, of a concrete mold therefore contains a vibration system normally consisting of eccentric weights mounted on a central shaft driven by electric or hydraulic motors. An example of a dry cast concrete pipe making machine using a vibration system is show in U.S. Pat. No. 4,708,621.
For optimum consolidation of the concrete products produced by the dry-cast method, it is desirable to have the vibration distributed evenly along the entire length of the mold. Many current systems make use of a separate vibration unit which is assembled outside of the core. These systems contain a central shaft or shafts, supported by a series of bearings, to which eccentric weights are fixed. The shaft assembly is mounted in a structural tube which is then fastened inside the core of a concrete mold. These vibration units are either driven by a directly mounted hydraulic or electric motor or by coupling to an external drive unit. These prior art vibration units are made so that they can be removed and placed in cores of other sizes, where adjustment of the eccentric weights may be required because cores of different masses require different vibration output for optimum performance.
In some other prior art systems, multiple electric vibrators are mounted inside the core and are coupled with shafts fastened to and supported by the vibrator shafts. This type of system requires suitable access to allow alignment and fastening of each vibrator and coupling shaft. In small diameter cores, limited access makes installation and removal of such systems difficult because when removing or replacing the electric vibrators, the coupling shafts must also be removed. There is therefore a need for an improved vibration system that will provide advantages over the existing prior art systems.